As with any building project, there were surprises -- more structural support needed; higher costs for installing skylights; unexpected questions from building department officials.

All the while, Jonathan Segal stood by, offering encouragement to his son and his signature as a cosigner with his wife Wendy to the $462,000 property purchase.

"I really wanted him to reap the benefits or accomplishments without anybody saying I had something to do with it," Jonathan said. "It was important for me that he be autonomous."

Matthew, who graduated from the University of Southern California architectural program in 2010, said he had driven past the post office numerous times and finally was able to buy it from a 93-year-old woman, who first listed it for $800,000.

"I wanted to do four to six units because that's only what I can afford to do," he said.

He built a two-story 1,200-square-foot townhouse above the parking lot in the rear and carved out two units of about the same size in the post office building. The rents are roughly $2,600 to $2,900 per month.

The new construction features a raw steel exterior that will oxidize to a warm brown or orange, a light-filled interior and large gathering space on the main floor.

The old building was gutted while leaving the orange ceiling beams and C Street facade largely intact. The front door still sports a "United States Postal Service" decal.

Segal incorporated an interior courtyard lined with galvanized metal to accentuate indirect sunlight and positioned the skylights so that residents won't have to turn on the lights for most of the day.

The exterior features a hedge of 43 ficus trees enclosing a private patio. Other landscaping incorporates water-wise succulents.

While savoring extra sleep and leisure time, Segal is on the hunt for another property to tackle even as he and has father tackle bigger projects in North Park. But he offers these lessons for other budding architects and builders:

"Credit cards are gold": "I just float stuff every month on my credit card -- I pay it off every month, but that extra 30- to -45-day window allowed me to get further along without borrowing as much money."

"Be really friendly with all the contractors": "Them supporting you and you supporting them is really important, because they have a vested interest in the property. It's not like another job. They actually care and are proud to be working on it."

Treasure that close relationship with your banker: "I got a loan through First Republic Bank... I don't know if I could have done it without him," he said, referring to loan officer Jason Keimer.

Post offices make good adaptive-reuse candidates: The La Jolla community is up in arms about the prospect that its post office is being put up for sale, but Segal said post offices occupy ideal sites, either for new development or new uses: "Typically they're in the center of an area with easy access for everybody and the focal point of a community. As a development, that's always important." The La Jolla postal branch, he ventured, would make "an incredible restaurant."

Segal lives in the new portion of Postal Lofts with two roommates, Courtney Rains and Hayley Johnston, and is searching for tenants for the front units.

"I think it's pretty fantastic," Rains, 25, said of her new home. "I like the space, the layout, the feel. I appreciate the open architecture of it all."

She said friends at the recent house warming heaped praise on Matthew's accomplishment

"All I heard was rave comments and positive reviews," she said. "There were no negative comments and everyone was very excited they were going to meet the architect."

Is this San Diego's newest "star-chitect"?

"I think he has all the talent and skills, resources, honest integrity to make the Segal name that much better," she said. "His dad is a fantastic architect. Matt has all the ability to be just as great, if not even greater."

Matthew calls his father "the Emperor" and Rains offered a moniker for the son: "Crown Prince."

Twenty years from now, she expects him to have pushed the limit on any number of developments.